Current sensor for measuring an electrical current in a circuit having a plurality of electrical conductors

ABSTRACT

The invention relates to a current sensor for monitoring electrical disturbances on an electrical circuit having an electrical conductor. The current sensor comprises a magnetic flux sensor for sensing a magnetic flux generated by a current flowing in the electrical conductor and for providing a signal representative of the current; and a processor for acquiring the signal from the magnetic flux sensor, for detecting an electrical disturbance on the current and for providing electrical disturbance data. The current sensor may also comprise a ring-shaped magnetic structure for receiving the electrical conductor and an opening within the ring-shaped magnetic structure for receiving the magnetic flux sensor. The magnetic flux sensor being for sensing a magnetic flux generated in the magnetic structure by the current in the electrical conductor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35USC§119(e) of U.S. provisionalpatent application 60/679,997, the specification of which is herebyincorporated by reference.

BACKGROUND

1) Field of the Invention

This application is related to the field of current sensors.

2) Description of the Prior Art

Stray currents, especially 60 Hz currents, flowing on the groundingnetwork of agricultural facilities may create zones of discomfort forthe animals and cause physiological reactions of the animals resultinginto abnormal health conditions.

The new technologies used to control electric motors which modify thelevel and the frequency of the current and the presence of electricalarcs on the distribution network of a farm are also among the factorsthat have direct consequences on the quality of the animal environment(see U.S. Pat. No. 6,690,565 B2).

Two types of variable speed motor controllers are frequently used inagricultural facilities. One is based on thyristors switched at a rateof 120 times per second while the other is composed of Insulated GateBipolar Transistor switched between 10000 and 20000 times per second.

The insulation of electric motor windings and also the insulation of theelectric cables feeding the motors have capacitive reactance componentsin regard to the ground. These capacitive reactance components areresponsible for current leaks when exposed to high frequency currents.The transmission modes of the leakage current are the same for the twotechnologies of motor controllers but the leakage will be more importantin the case of the technology operating at higher frequencies.

The electrical arcs, in addition to being responsible of many fires,have important consequences on the animal environment because theyproduce harmonics of various levels and frequencies on the groundingnetwork. Since electrical arcs may arise in every component ofelectrical networks, it is thus useful to monitor each component inorder to perform early detection, characterize and predict any possiblefault.

SUMMARY

One aspect of the invention provides a current sensor for monitoringelectrical disturbances on an electrical circuit having an electricalconductor, said current sensor comprising: a ring-shaped magneticstructure for receiving said electrical conductor whereby the magneticstructure can be positioned along said electrical conductor; a magneticflux sensor for sensing a magnetic flux generated in said magneticstructure by a current flowing in said electrical conductor and forproviding a signal representative of said current; said ring-shapedmagnetic structure comprising an opening for receiving said magneticflux sensor; and a processor for acquiring said signal from saidmagnetic flux sensor, detecting an electrical disturbance on saidcurrent and providing electrical disturbance data.

A current sensor for detecting an electrical disturbance in anelectrical circuit having an electrical conductor, said current sensorcomprising: a magnetic flux sensor for sensing a magnetic flux generatedby a current flowing in said electrical conductor and providing a signalrepresentative of said current; and a processor for acquiring saidsignal from said magnetic flux sensor, detecting said electricaldisturbance on said current and for providing an electrical disturbancesignal.

Another aspect of the invention provides an electrical disturbancemonitoring system, comprising: a plurality of current sensors eachassociated with an electrical conductor and an identifier, each having amagnetic flux sensor for sensing a magnetic flux generated by a currentflowing in said electrical conductor and for providing a signalrepresentative of said current; and a processor for acquiring saidsignal from said magnetic flux sensor, for detecting an electricaldisturbance on said current and for providing electrical disturbancedata; a networking module for combining data provided by said pluralityof current sensors; and a processing module for receiving and foranalyzing the combined data, for monitoring and for locating, using saididentifier, said electrical disturbance and for alerting in case ofabnormal situations.

Another aspect of the invention provides a current sensor comprising aring-shaped magnetic structure for receiving an electrical conductorwhereby the magnetic structure can be positioned along the electricalconductor; a magnetic flux sensor for evaluating a magnetic fluxgenerated by a current flowing in the electrical conductor; an openingwithin the ring-shaped magnetic structure for receiving the magneticflux sensor; a data acquisition module for receiving a reading from themagnetic flux sensor concerning the current. Preferably, the currentsensor comprises a plurality of ring-shaped magnetic structures,magnetic flux sensors and openings and wherein each of the plurality isfor one of a plurality of electrical conductors.

Additionally, the current sensor can comprise a global ring-shapedmagnetic structure surrounding all of the plurality of ring-shapedmagnetic structure; and a global magnetic flux sensor for evaluating amagnetic flux generated by currents flowing in all the electricalconductors. A differential reading of current flowing in each conductorcan then be measured.

The reliability of the measurements is independent of the location ofthe current sensor since its unique design makes it insensitive tosurrounding electromagnetic fields. Also, the size of the orifices wherethe conductors are inserted is chosen according to the size of theconductors to insure a perfect fit and thus eliminate any positioningreading error.

The proximity between the Hall Effect sensors and the signal processoreliminates the error usually caused by the length and the impedance ofthe conductors between the reading instrument and the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will becomeapparent from the following detailed description, taken in combinationwith the appended drawings, in which:

FIG. 1 is an exploded view of the current sensor in accordance with anembodiment of the invention;

FIG. 1A is a perspective view of the top portion of the casing of thecurrent sensor of FIG. 1;

FIG. 1B is a perspective view of the individual magnetic structures foreach conductor of the current sensor of FIG. 1;

FIG. 1C is a perspective view of the printed circuit along with themagnetic flux sensors, the voltage detector and the processor of thecurrent sensor of FIG. 1;

FIG. 1D is a perspective view of the global magnetic structure for allfour conductors of the current sensor of FIG. 1;

FIG. 1E is a perspective view of the bottom portion of the casing aswell as the retaining shoulders for the components of the current sensorof FIG. 1;

FIG. 2A and FIG. 2B are plan views of the current sensor of FIG. 1;

FIG. 3 is a graph illustrating a line current;

FIG. 4 is a graph illustrating a current inrush;

FIG. 5 is a graph illustrating load variations of a circuit;

FIG. 6 is a graph illustrating the current of a non-linear load;

FIG. 7A is a graph illustrating the current of a single phase PWM typemotor controller;

FIG. 7B is a graph illustrating the current of a three-phase PWM typemotor controller;

FIG. 8 is a graph illustrating the harmonics generated by an electricalarc;

FIG. 9A is a block diagram showing current sensors locations in anelectrical distribution panel according to an embodiment of theinvention;

FIG. 9B is a block diagram showing a current sensor arrangement for thecomplete monitoring of a distribution panel according to an embodimentof the invention;

FIG. 10 is a block diagram showing localisations of current sensors onelectrical networks according to an embodiment of the invention;

FIG. 11 is a block diagram showing a typical network architectureaccording to an embodiment of the invention;

FIG. 12 is a block diagram showing the electrical connections in anintrusive current sensor according to an embodiment of the invention;and

FIG. 13 is a block diagram showing a possible use of an intrusif currentsensor according to an embodiment of the invention.

It will be noted that throughout the appended drawings, like featuresare identified by like reference numerals.

DETAILED DESCRIPTION

According to an embodiment, the present invention may perform highresolution current measurements and recordings of transient phenomena(amplitude, frequency).

According to an embodiment, the present invention may provide the userwith a tool which generates an electrical signal. From the spectralanalysis of the electrical signal, it will be possible to identify anyelectrical disturbance likely to affect the electrical equipment,prevent against animals health issues related to the presence of currentin their environment and protect the assets by early detection ofpossible electrical causes of fire.

The exploded view of an embodiment shown in FIG. 1 shows the arrangementof the printed circuit 31 and the components in accordance with anembodiment of the invention. FIGS. 1A to 1E are enlarged views of eachportion of FIG. 1.

The current sensor of FIG. 1 captures signals and can convert the valuesinto specific digital formats and also offers digital communicationfunctionalities.

The current sensor components are all included in a casing 1. Thecurrent sensor 100 is designed to carry all the conductors (line andneutral) of a specific circuit. Each conductor (not shown) will passthrough an individual input hole 2, 3, 4 and 5, allowing for an analysisof each conductor current characteristics. Inputs number 2, 3 and 4 arededicated to the line conductors while input number 5 is for the neutralconductor. The diameter of these inputs is adapted to the conductordiameter which permits to avoid the influence of the surroundingelectromagnetic fields generated by other current carrying conductors orequipment. It should be noted that it would be possible to create acurrent sensor adapted to receive any number of conductors, even agrounding conductor. In an embodiment, there will be three lineconductors and one neutral conductor.

The casing 1 is composed of two sections. The bottom section 1B ismoulded to receive and organize all the components of the currentsensor. The top section 1A acts as a cover; it protects and holds thecomponents in place.

Small ferrites and/or other magnetic material 6, 7, 8 and 9, sizedaccording to the size of the electrical conductor are used. An opening10, 11, 12 and 13 is practiced in the magnetic structure to receivemagnetic flux sensors 14, 15, 16 and 17, Hall effect sensors forinstance.

Each magnetic structure 6, 7, 8 and 9 is machined to obtain a preciseopening 10, 11, 12 and 13. These openings 10, 11, 12 and 13 insure theconsistency of the magnetic flux and guaranty the precision of themagnetic flux sensors 14, 15, 16 and 17.

Another aspect of the current sensor shown in FIG. 1 is the positioningof the magnetic structure 6, 7, 8 and 9 and its protection. Positioningand keeping in place a magnetic structure 6, 7, 8 and 9 is complex whenthe work is done manually with the use of glue. The retaining shoulders19, 20, 21 and 22 maintain the magnetic structures 6, 7, 8 and 9 andmagnetic flux sensors 14, 15, 16 and 17 simply and precisely.

The magnetic structures 6, 7, 8 and 9 are protected from the electricalconductors (not shown) by the retaining shoulders 19, 20, 21 and 22.These retaining shoulders are machined according to the magneticstructures 6, 7, 8 and 9 dimensions. The magnetic structures 6, 7, 8 and9 are aligned with the magnetic flux sensors 14, 15, 16 and 17 and gluedfor protection.

A printed circuit 31 is used to position the magnetic flux sensors 14,15, 16 and 17 into the openings 10, 11, 12 and 13 of the magneticstructures 6, 7, 8 and 9 before the whole is glued.

As mentioned earlier, the Hall Effect sensor, compared to regularcurrent transformer, offers a greater frequency range. It makes possiblethe spectral analysis of low and medium frequencies.

According to an embodiment of the invention, another aspect of thecurrent sensor consists of using small ferrites and/or other magneticmaterial 23, sized according to the current sensor diameter. An opening24 is performed in the magnetic structure 23 to receive a magnetic fluxsensor 18.

This magnetic structure 23, with the use of a magnetic flux sensor 18will perform the reading of currents in differential mode when the linecurrents are important. All the line conductors 2, 3, 4 and 5 will passthrough this magnetic structure 23.

In this embodiment, the magnetic structure 23 is machined to obtain aprecise opening 24. This opening 24 ensures the consistency of themagnetic flux and guaranties the precision of the magnetic flux sensor18.

Positioning and keeping in place a magnetic structure 23 is complex whenthe work is done manually with the use of glue. The retaining shoulder32 maintains the magnetic structure 23 and magnetic flux sensor 18simply and precisely. The magnetic structure 23 is protected from theelectrical conductors 2, 3, 4 and 5 (not shown) by the retainingshoulders 19, 20, 21, 22 and 32. The magnetic structure 23 is alignedwith the magnetic flux sensor 18 and glued for protection. A printedcircuit 31 is used to position the magnetic flux sensor 18 into theopening 24 of the magnetic structure 23 before the whole is glued.

The following should be noted for Hall Effect sensors used as magneticflux sensors in this embodiment of the invention. When the excitationcurrent is held constant, the output voltage is proportional to themagnetic field produced by the current being sensed or measured. Halleffect sensors generally include a constant current source, a gappedtoroid core and a hall effect generator extending into the gap of thecore. Positioning of the hall effect generator within the gap isimportant because inaccurate and unsteady positioning of the hall effectgenerator within the gap may result in the hall effect sensormalfunctioning.

Additionally, environmental factors may also impact the properfunctioning of the hall effect sensor. More particularly, outsidecontaminants (e.g., dust, dirt, grime, oil, fluids) may hinder theoperation of the hall effect sensor.

In view of the above, there is a need for a packaging arrangement thatprovides for secure and stable positioning of the hall effect generatorinside the air gap of the hall effect sensor, which the presentarrangement solves. It also insulates the hall effect sensor from animpeding effect on the sensor resulting from contaminants.

In the case where no retaining shoulders are used, since the Hall effectsensor is introduced in the air gap and that the air gap is slightlylarger than the size of the Hall effect sensor, there will be a smallloss of linearity of the value measured. Therefore, during calibrationof the sensor, each Hall Effect sensor will be linearized by adjustingthe calibration within the software used to collect the data andpotentially interpret it.

Although this embodiment is described with the use of Hall Effectsensors, it should be noted that any magnetic flux sensor, notnecessarily a hall effect sensor, can be used. For example, the magneticflux sensor could be a magnetoresistivity sensor. The arrangement of thecomponents would be the same even though an extra connection would beneeded and the current draw of the magnetoresistivy sensor is higherthan that of the Hall effect sensor.

A processor 29, a Digital Signal Processor for instance, is located at amiddle position between the electrical conductors inputs 2, 3, 4 and 5in order to limit the voltage drop and the disturbances between themagnetic flux sensors 14, 15, 16, 17 and 18 and the processor 29. Themagnetic flux around the electrical conductors 2, 3, 4 and 5 areconverted into proportional analog signals by the magnetic flux sensors14, 15, 16 and 17 and the differential magnetic flux, corresponding tothe differential current in electrical conductors in inputs 2, 3, 4 and5, is converted into a proportional analog signal by the magnetic fluxsensor 18. These signals are transmitted to the DSP 29 which processesand converts the analog signals into digital signals.

Although it is possible to have an analog output of the signalscaptured, a digital output is preferred because analog outputs tend tobe affected by the neighbouring magnetic flux, which could causereliability and precision errors in the transmitted data.

The detection of voltage in the conductors will be done by a coppertrace 25, 26, 27 and 28 located directly on the printed circuit 31. Thecopper trace is shaped like a half moon around the electrical conductorinputs 2, 3, 4 and 5. This copper trace 25, 26, 27 and 28 will act as anantenna. The voltage sensed by the copper traces will be transmitteddirectly to the signal processor 29 by the printed circuit 31. Theprocessor 29 will be able to confirm the absence of voltage on each lineindividually 2, 3, 4 and 5.

Any shape or material which could sense a magnetic flux and thereforedetect the presence of a voltage in the conductors can be used.Preferable, the choice of shape and material creates an antenna, as withthe copper half-moon trace.

The connector 30 serves for both the power of the electronic circuitsand the data transmission.

It will be understood that the invention is not limited to the specificforms shown and/or described. For example, the core may have a varietyof configurations and sizes including rounded or bevelled lead-insurfaces and interlocking dimples to help hold the laminations together,at least during manufacture; the hall generator preferably is centeredwith respect to the core faces and oriented generally perpendicular withrespect to the conductor, but those parameters may be altered; thematerials utilized in forming the conductor, the core and the circuitboards may be varied depending on the specific application; a widevariety of primary printed circuit boards may be utilized depending onthe specific application and environment in which the sensor system isutilized; and the sensor systems may be combined with a variety of otherfeatures within a given component.

In a simple expression, the current sensor therefore comprises aring-shaped magnetic structure for receiving an electrical conductorwhereby the magnetic structure can be positioned along the electricalconductor, a magnetic flux sensor for evaluating a magnetic fluxgenerated by a current flowing in the electrical conductor; an openingwithin the ring-shaped magnetic structure for receiving the magneticflux sensor; and a data acquisition module for receiving a reading fromthe magnetic flux sensor concerning the current. In this simpleembodiment, the sensor is used to measure current of only one conductor.

In another simple embodiment, the current sensor comprises a pluralityof ring-shaped magnetic structures, magnetic flux sensors and openingsand each of the plurality is used for one of a plurality of electricalconductors. This is the case where a sensor for four conductors isbuilt, as is shown in FIG. 1.

When the sensor is to be used with more than one conductor, itpreferably includes a global ring-shaped magnetic structure surroundingall of the plurality of ring-shaped magnetic structure; and a globalmagnetic flux sensor for evaluating a magnetic flux generated bycurrents flowing in all said electrical conductors. A differentialreading of current flowing in each conductor can then be measured.

The plan view shown in FIG. 2A shows the dimensions and arrangement ofthe components in accordance with an embodiment of the invention.

In a particular embodiment, the current sensor is intended to receivefour electrical conductors (three phase circuit with neutral, 3θ-4 W).The diameter (D) of the electrical conductor input holes 2, 3, 4 and 5is determined according to the electrical conductor diameter to beinserted in the sensor body. The magnetic structures 6, 7, 8 and 9 usedin the present model is made by Panasonic, the model number isKR16TT18106 and the dimensions are 18 mm OD, 10 mm ID, 6 mm HT. Thewidth of the retaining shoulder 19, 20, 21 and 22 is illustrated by the“F” dimension of FIG. 2A. The top part (cover) 1A of the sensor holdsthe magnetic structures 6, 7, 8 and 9 in place with an internal andexternal shoulder.

The magnetic flux sensors 14, 15, 16 and 17 are inserted in openings 10,11, 12 and 13 and are kept in place with the use of glue. The magneticflux sensors 14, 15, 16 and 17 used in the present model are made byAllegro Microsystems inc. They are part of the A132X model family andthe dimensions are 4.04 mm OD, 1.47 mm ID, 3.10 mm HT. The dimension ofthe openings 12, 11, 12, 13 and 24 in the magnetic structures isindicated by the “E” dimension of FIG. 2A.

The plan view shown in FIG. 2B shows the dimensions and arrangement ofthe components for a differential reading of leakage currents inaccordance with an embodiment of the invention. In an embodiment, thesensor 100 is intended to receive the four electrical conductors (notshown) for an analysis in differential mode. The magnetic structure 23used in the present model is made by Magnetics, the model number is54-454-1-E and the dimensions are 44,45 mm OD, 31,8 mm ID, 3.18 mm HT.The width of the retaining shoulder 32 is illustrated by the “G”dimension of FIG. 2A.

The magnetic flux sensor 18 is inserted in opening 24 and is kept inplace with the use of glue. The magnetic flux sensor 18 used in thepresent model is made by Allegro Microsystems inc. It is part of theA132X model family and the dimensions are 4.04 mm OD, 1.47 mm ID, 3.10mm HT. The dimension of the opening in the magnetic structure isindicated by the “E” dimension of FIG. 2A.

It should be understood that the above given dimensions are meant to beexemplary only and that any other dimensions adapted to the electricalconductors on which the current sensor is to be installed could also beused.

The Hall Effect sensors along with the magnetic structures permit tomeasure the signal frequency, the amplitude and the harmonic content inrelation with the line and the neutral conductors.

FIG. 3 shows an electric motor current inrush at start-up. Section A ofFIG. 3 shows the amplitude of the current and the duration of the inrushwhile part B shows the value of the current during steady-stateoperation.

In section C of FIG. 4 we can see a sudden current inrush usuallygenerated by a mechanical problem.

The total load of a distribution can be monitored by installing a sensoron the main conductors of the entrance. FIG. 5 gives an example of theevolution of the load on a distribution. Section A shows a steady statevalue of current on the distribution. Section B would be created by thestart-up of a motor for example, followed by section C showing thesteady state current including the motor. Section D shows that anadditional load has been turned ON.

The current sensor offers two possibilities for the measurement ofleakage current. The first method consists in computing the leakagecurrent from the values measured by the Hall Effect sensor of eachconductor. The second option is to obtain the value of the leakagecurrent from the outer Hall Effect sensor including all the conductors.The first method will be preferred in the case of small line currents.

The leakage current spectrum is mostly similar to the line currentspectrum.

FIG. 6 shows the shape of the current generated by a variable speedmotor drive using the thyristor technology (120 Hz switching).

FIGS. 7A and 7B show the difference between the shapes of the currentsgenerated by single phase (7A) and three phase (7B) PWM motor drives(PWM=IGBT transistors, 10 KHz-20 KHz).

FIG. 8 shows the shape of the load current of an electrical equipmentwhich has a fault on a conductor (bad joint). The signal is composed oflow and medium frequencies with random shapes.

The current sensor can be used in many ways. Its location is chosenaccording to the monitoring needs.

FIG. 9A shows an electrical panel 33 of a building. The panel 33 is fedby four conductors 35, 36, 37 and 38 installed inside a conduit; theline conductors 35 and 36, the neutral conductor 37 and the groundingconductor 38. The line conductors 35 and 36 and the neutral conductor 37are inserted in the current sensor 42. From this location, it ispossible to analyze the current spectrum, detect the presence ofharmonics and identify their sources (what type of non-linear loads),detect the presence of electrical arcs and measure the value of theleakage current (resistive or capacitive). The preceding informationconcerns the whole building distribution since the sensor is installedon the main conductors. When current sensors are installed on thecircuits of the distribution panel 33, the same information is availablefor each circuit 41 monitored by a sensor.

FIG. 9B shows the sensor 42 and 43 arrangement for the completemonitoring of a distribution panel 33, one sensor 42 on the mainconductors and one sensor 43 on each circuit leaving the panel.

FIG. 10 shows a circuit of an electrical distribution 46 feeding a motor47. The current sensor 48 is placed between the motor starter 49 and themotor 47. From this location, the sensor can provide informationconcerning the condition of the fuse or the overload 50, the conditionof the contacts 51 of the contactor 49, the presence of electric arcsgenerated by a worn contact 52 of the contactor and also the value ofthe leakage current. Moreover, this new generation of current sensor canbe part of an integrated management system, an energy monitoring systemor a fire alarm system for example.

As shown in FIG. 11, the current sensor 53 can be located on the maindistribution. Moreover, each circuit 54, 55 and 56 may carry a currentsensor 57, 58 and 59. All the sensors 53, 57, 58 and 59 are connected toa hub 60.

The hub 60 is connected to an Ethernet network 61. The data transmittedby the current sensors 53, 57, 58 and 59 can be analysed by a computersystem 62, a laptop computer 63, or a dedicated monitor 64. For anexternal link, the current sensor 53, 57, 58 and 59 can be linked to acomputer system 66 by modem 65.

The present current sensor can be used in any environment wheredetection of currents, especially stray currents, is needed.

The potential applications for the agricultural domain, without beinglimited to, may apply to the following electrical equipment: the mainelectrical distribution, the distribution panels, the distributioncircuits or the motors.

For a personalized management of the electrical network, the sensor canbe installed at the Voluntary Milking System (milking robot), at thepulsator heads controller, at the water pump controller, at powersupplies, in portable milkers, in the feed control panel or in thestable cleaner controller, for instance.

The current sensor, for whatever purpose it may serve, may be used inthe commercial and industrial sectors. The electrical networksconfigurations of dairy facilities of more than 100 cows are similar inevery aspect to the ones found in these sectors.

In the residential sector, in addition to its application for the loadsin general, this current sensor has a competitive advantage on thearc-detecting circuit breaker and could be used advantageously.

Nowadays, electrical equipment safety is an important financial andsocial issue all around the world. Heteroclite development in numerouscountries, free access to electrician profession and lack of controlsystems played a role in the emergence of hazardous equipments.

As previously mentioned, according to an embodiment, a current sensorincludes a programmable circuit, as a processor, providing computingfaculties for considering some relevant derivatives and magnitudes.Associating thresholds to each type of perturbations provides managementand priorisation of the possible reaction commands including loadshedding.

FIG. 12 is a block diagram showing the main components and theelectrical connections in an intrusive current sensor, according to anembodiment of the invention. In this embodiment, the intrusive currentsensor is mounted on a printed circuit 67. The electric circuitconductors (not shown) are connected to inputs/outputs 71, 72, 73, 74.The current sensor individually receives a line conductor connected tothe input/output 71, 72 and a ground conductor connected to theinput/output 73, 74 such that current in each conductor can be analysedindividually. The intrusive current sensor could alternatively beadapted to receive only one conductor or more than two conductors suchas three line conductors and one neutral conductor for three-phaseapplications, for example.

The processor 75 is positioned on the printed circuit 67 proximate themagnetic flux sensors 68, 69 in order to minimize voltage drop andinterferences. The magnetic flux sensors 68, 69 converts the magneticflux created by the current flow in the conductors into an analogsignal. The analog signal is then directed to the processor 75 foranalysis. The processor 75 detects electrical disturbances on thecurrent and provides an electrical disturbance signal to control anon/off switch 70, a TRIAC or a contactor for instance, for disconnectingthe load in reaction to a command from the processor 75. A power supply76 is also included to power the sensor.

In this embodiment, the magnetic flux sensors 68, 69 are intrusive Halleffect sensors of model ACS704ELC-015 from Allegro but it iscontemplated that non-intrusive Hall effect sensors and that other typesof magnetic flux sensors, as magnetoresistive sensors, may alternativelybe used.

The magnetic flux sensor and the circuit boards may be varied dependingon the specific application; a wide variety of primary printed circuitboards may be utilized depending on the specific application andenvironment in which the sensor system is utilized; and the sensorsystems may be combined with a variety of other features within a givencomponent.

It should be appreciated that the intrusive current sensor may comprisevoltage detectors (not shown) connected in parallel with magnetic fluxsensors 68, 69 or connected between the inputs 71, 73 to measure adifferential voltage.

FIG. 13 illustrates a possible use of an intrusive current sensor. Atable fan 80 is plugged in a house power outlet 77. A current sensor 78is located at the fan electrical connection 79, preferably inside thefan 80. The current sensor 78 checks for abnormal operation of the fan80 by detecting an occurrence of an electrical disturbance such as anelectric arc, overload and underload. The fan 80 can be disconnectedusing the on/off switch 70 under specific conditions.

This new type of current sensor is adapted to analyse a serial, aparallel or a differential default and eventually initiate a reactioncommand on the electrical circuit.

The embodiments of the invention described above are intended to beexemplary only. The scope of the invention is therefore intended to belimited solely by the scope of the appended claims.

1. A current sensor for measuring an electrical current on an electricalcircuit having a plurality of electrical conductors, said current sensorcomprising: a plurality of ring-shaped magnetic structures each forreceiving one of said electrical conductors whereby the magneticstructures can be positioned along said electrical conductors, and eachhaving an opening therein receiving a magnetic flux sensor forevaluating a magnetic flux generated by a current flowing in said one ofsaid electrical conductors and for providing a signal representative ofsaid current; a global ring-shaped magnetic structure surrounding saidplurality of electrical conductors; and a global magnetic flux sensorfor evaluating a magnetic flux generated by currents flowing in saidplurality of electrical conductors to measure a differential reading ofcurrent flowing in said plurality of electrical conductors.
 2. Thecurrent sensor as claimed in claim 1, wherein the magnetic flux sensorsare hall effect sensors.
 3. The current sensor as claimed in claim 1,further comprising retaining means for retaining said magneticstructures and the magnetic flux sensors around said electricalconductors.
 4. The current sensor as claimed in claim 1, furthercomprising voltage detectors each for detecting a voltage of acorresponding one of said electrical conductors.
 5. The current sensoras claimed in claim 4, wherein said voltage detectors are shaped in ahalf moon each surrounding said corresponding one of said electricalconductors and said voltage detectors each comprises a conductive traceon a substrate for generating a voltage signal if voltage is present insaid corresponding one of said electrical conductors, and wherein thevoltage signals are received by said data acquisition module.
 6. Thecurrent sensor as claimed in claim 1, further comprising a case throughwhich said electrical conductors can be inserted for protecting saidmagnetic structures, said magnetic flux sensors and said dataacquisition module.
 7. The current sensor as claimed in claim 1,comprising an analog to digital converter for converting a readingreceived by said data acquisition module into digital sensor data. 8.The current sensor as claimed in claim 7, further comprising an emitterfor transmitting said digital sensor data.
 9. The current sensor asclaimed in claim 1, wherein said global magnetic flux sensor is a halleffect sensor.
 10. The current sensor as claimed in claim 1, furthercomprising retaining means for retaining said global magnetic structureand said global magnetic flux sensor around said plurality of magneticstructures.
 11. The current sensor as claimed in claim 1, wherein saidplurality of electrical conductors has four electrical conductors. 12.The current sensor as claimed in claim 11, wherein said electricalconductors are three line conductors and one neutral conductor.
 13. Thecurrent sensor as claimed in claim 1, further comprising a dataacquisition module for receiving a reading from said magnetic fluxsensors.